1. Field of the Invention
The present invention relates generally to over the road freight vehicles, and more specifically to a novel construction for the rear door frames of large vans and semitrailers. The present rear door frame construction enables a trailer manufacturer to install a single door frame configuration which may be readily adapted to either swinging doors or to an overhead roller door, without requiring a door frame dedicated to each type of door.
2. Description of the Related Art
The trailer manufacturing industry has generally developed certain conventional and specific configurations for various trailer components. While certain differences exist between different trailers, manufacturers have universally tended to construct trailer frames and other components of a relatively large number of relatively simple angle, channel, and other shapes.
Such construction is relatively economical in terms of the materials required, as it requires only a relatively few different readily available stock cross sectional shapes. However, the components must be welded or otherwise assembled together to form the required shapes, and then the finished lengths (posts, headers, sills, etc.) must in turn be assembled to complete the structure. Thus, any savings in material is likely canceled by the labor intensive welding process required to form two or perhaps more linear welds along the length of the frame component assembly. Moreover, the additional time required to fabricate such subassemblies obviously adds considerably to the time required for the construction of a given trailer. The additional labor required for conventional construction results in greater opportunity for error, and resulting requirement for reworking or discarding the improperly constructed component. In addition, such subassemblies constructed of a series of separate stock shapes tend to be heavier than alternative constructions formed of single prefabricated components, and the welds in those built-up subassemblies result in components that are weaker than components formed of single prefabricated lengths of material.
Another problem with conventional trailer frame construction is the development of different frame configurations for different types of trailer doors, as noted further above. A purchaser of a trailer is to a great extent committed to the specific type of door (side hinged or overhead) with which the trailer was originally equipped, regardless of subsequent need or desire.
While it is possible to modify or retrofit a trailer with a different type of door than that with which it was originally manufactured, the process is quite involved, time consuming, and costly. Generally, the rear frame for side hinged doors does not include any means for the installation of lateral tracks or channels for an overhead door, and the frame header does not provide sufficient depth for the mechanism of the overhead door. The frame for an overhead door generally incorporates the lateral door tracks or channels integrally therewith, with the header being relatively deep for the overhead door mechanism. While most customers might prefer side hinged doors due to the higher and slightly wider openings provided, overhead doors might be preferable in certain circumstances, depending upon the space available where the trailer is frequently docked, and other considerations. In any event, once the decision is made as to the type of door to be installed upon a given trailer, it is very difficult to change that door type to an alternative type.
Accordingly, a need will be seen for a universal rear door frame for semitrailers, large vans, and the like, which frame is essentially identical for all trailers and door types. While the present frame may be initially configured for use with side hinged doors, it is a relatively simple matter to fit additional door tracks to the existing door frame to allow the frame to support an overhead door instead. Moreover, the installation of the tracks to the forward surfaces of the side posts and the elimination of the relatively deep header, result in an overhead door having an opening essentially equal to that of the side hinged door, thereby permitting taller and wider loads to be placed in the trailer equipped with the present rear door frame and overhead door. The ease of construction, economy, and versatility of the present universal door frame result in significant advances over other door frames and door installations of the related art.
A discussion of the related art of which the present inventor is aware, and its differences and distinctions from the present invention, is provided below.
U.S. Pat. No. 3,140,116 issued on Jul. 7, 1964 to William D. Speas, titled xe2x80x9cSide-Loading Vehicle,xe2x80x9d describes a trailer in which the side panels and roof are supported upon telescoping vertical posts. The posts may be extended to raise the side panels partially, with the side panels then rolling upwardly to overlap immediately beneath the roof, in order to complete the raising of the sides. Speas does not disclose any specific structure for the conventional appearing rear door frame of his trailer, with its apparently conventional side hinged doors.
U.S. Pat. No. 3,211,493 issued on Oct. 12, 1965 to Richard M. Mandel, titled xe2x80x9cBulkhead Structure,xe2x80x9d describes various structures providing reinforcement for side hinged and overhead rear doors in trailers and the like. Mandel provides a series of horizontal reinforcements for side doors and vertical reinforcements for overhead doors, in order to reduce damage to such doors due to shifting cargo. Mandel does not disclose any specific structure for the rear door frame of his trailer.
U.S. Pat. No. 3,292,803 issued on Dec. 20, 1966 to Lyle D. Keller et al., titled xe2x80x9cSemi-Trailer,xe2x80x9d describes a trailer having side hinged front doors and a system for lowering the front of the trailer for loading and unloading the trailer where no dock or ramp is available. Keller et al. provide a pneumatic interlock for the doors in order to assure that the trailer brakes remain locked while the doors are unlocked or open. However, Keller et al. do not specify any particular configuration for the frame of the doors for their trailer, nor do they disclose the adoption of an overhead type door with their trailer.
U.S. Pat. No. 4,652,042 issued on Mar. 24, 1987 to Samuel M. Bader, titled xe2x80x9cDesign Column And Door System For Highway Trailers,xe2x80x9d describes a trailer having a series of telescoping door panels disposed between a series of actuating columns. Each column includes a multiple section telescoping cylinder, to which the edges of adjacent doors are attached. Actuating the cylinders lifts the lower edges of the doors, causing the sections to telescope into one another. This system is not truly an overhead door, in that no tracks extend into the roof for the door, nor is there any provision for side hinged doors in the Bader trailer. Accordingly, Bader does not disclose any specific structure for the universal use of either side hinged or overhead doors, as provided by the present invention.
U.S. Pat. No. 4,659,132 issued on Apr. 21, 1987 to Gerald G. Day, titled xe2x80x9cConvertible Beverage Body For Delivery Truck Or Trailer,xe2x80x9d describes a trailer having a series of overhead doors installed along the sides and rear of the trailer. The interior of the trailer includes a series of movable panels, providing for side loading of the trailer from ground level or rear loading of the trailer from a raised dock or the like. The Day trailer includes a pair of hinged rear panels which swing inwardly, rather than outwardly as in conventional side hinged doors. The inwardly swinging panels, as well as the other partitions and internal structure, result in considerably less interior volume than available in a trailer utilizing the present rear door frame and side hinged or overhead door therewith. In any event, Day does not disclose any specific structure for either the side or rear door frames or posts in his trailer.
U.S. Pat. No. 4,669,775 issued on Jun. 2, 1987 to Robert S. Mathers, titled xe2x80x9cRoller Curtain For Truck Bodies,xe2x80x9d describes a moistureproof curtain or sheet which is extended from an overhead roller just inside the conventional side hinged doors of a truck trailer or van. The Mathers curtain precludes the entrance of moisture into the lower pressure generated within the trailer or van body when the vehicle is in motion. The device does not extend into the roof, as does an overhead door, but rather rolls up on a roller installed just inside the rear door header of the trailer or van. Mathers does not disclose any specifics regarding the construction of the rear door frame of the trailer or van.
U.S. Pat. No. 4,943,110 issued on Jul. 24, 1990 to John V. Pastva, titled xe2x80x9cCurtainside Truck Trailer Access System And Lock Assembly,xe2x80x9d describes various improvements in latching mechanisms for side curtain type trailers, wherein a flexible curtain or curtains extend along the side of the trailer to allow access through essentially the entire side of the trailer. The rear doors of the trailer disclosed are of the conventional side hinged type. Pastva makes no disclosure of any specific configuration of rear door frame for his trailer.
U.S. Pat. No. 4,952,009 issued on Aug. 28, 1990 to Elton E. Mountz et al., titled xe2x80x9cCurtained Doors For Vehicle Bodies,xe2x80x9d describes various improvements in attachment and tensioning means for such side curtains, providing horizontal and vertical tightening and security for such curtains. No disclosure is made of any form of side hinged or overhead door system, or door frame for such doors.
U.S. Pat. No. 5,192,176 issued on Mar. 9, 1993 to Hardy G. Roberts, titled xe2x80x9cSectional Van Trailer Having Detachable, Interchangeable Compartments Capable Of Forming A Continuous Van Body With Accompanying System For Forming Shelf Decks And Partition Walls Within Cargo Holding Sections,xe2x80x9d describes a series of modular compartments for removable installation on a trailer frame or the like. The compartments may be joined with intervening walls folded away to form a single, longer compartment if so desired. However, Roberts does not disclose any form of universal door frame for his compartments to provide for either side hinged or overhead doors.
U.S. Pat. No. 5,501,503 issued on Mar. 26, 1996 to Henry Thayer, titled xe2x80x9cVehicular Door,xe2x80x9d describes an overhead door in which the tracks and rollers are installed to the outside of the trailer. While this responds to the problem of a conventional overhead door and tracks taking up interior volume within the trailer, it creates the further problem of contamination and jamming of the track due to ice, snow, fallen leaves, and other debris. The present invention avoids this problem by installing the overhead door tracks (where used) within the trailer interior, but provides a universal door frame for installation of either side hinged doors or an overhead door, as desired.
U.S. Pat. No. 5,704,676 issued on Jan. 6, 1998 to John A. Hill, titled xe2x80x9cMulti-Temperature Cargo Transportation Apparatus,xe2x80x9d describes a trailer having a series of movable partitions therein. The partitions may be placed as desired to divide the trailer interior into two or more compartments of variable size as desired, with the system further providing for selective heating or cooling of one or more of the compartments. The Hill trailer utilizes a series of three side hinged doors which open into three separate compartments. The side hinged doors are placed forwardly of a single overhead door, with the side hinged doors and overhead door each having a different door frame structure. The Hill trailer teaches away from the present invention, in that (1) it requires two separate door frames for the door structure, and (2) it precludes placement of relatively large cargo within the trailer due to the series of separate side hinged doors and partitions.
Finally, British Patent Publication No. 2,152,448 published on Aug. 7, 1985 to Fruehauf Corporation (USA), titled xe2x80x9cGull-Wing Door Trailer,xe2x80x9d describes a trailer construction in which each side comprises a single openable panel formed by the side wall and one half of the roof. A hinge line extends down the center of the roof, with each side wall and roof half being selectively lifted by a series of hydraulic jacks or rams. The ""448 British Patent Publication makes no disclosure of any specific form of rear door frame, particularly one accommodating either side hinged doors or an overhead door, as provided by the present invention.
None of the above inventions and patents, either singly or in combination, is seen to describe the instant invention as claimed.
The present invention comprises a universal rear door frame for semitrailers, vans, and other similar cargo vehicles. Heretofore, conventional procedure has been to construct different door frames for either side hinged doors or overhead doors, depending upon the wishes of the customer. This leads to additional time required for construction, due to the different fixtures required for each door, additional stock inventory, etc. Moreover, such conventional door frames are constructed of a series of stock metal shapes (angles, channels, etc.) in order to save money in comparison to the cost of more complex fabricated shapes. However, this leads to additional costs for the labor required to fabricate frames from such a relatively large number of components.
The present invention responds to the above problem by providing a single door frame configuration adapted for use with either side hinged or overhead doors. Hinges may be provided along the rearward surfaces of the frame posts, while overhead door tracks may be provided along the forward surfaces of the posts in the event that an overhead door installation is desired. The basic frame structure remains the same in either case. In addition, the construction of the present frame is much more straightforward than truck trailer door frames of the prior art, which are formed of a series of stock shapes. The present frame utilizes a single square or rectangular section component for each side post and a second single channel component for the header, thus obviating any requirement for seam welding plural components together along their lengths to form the desired post or header component.
Accordingly, it is a principal object of the invention to provide an improved universal door frame for trailers, vans, and the like, comprising a single frame configuration adaptable for use with either side hinged or overhead doors as desired.
It is another object of the invention to provide an improved universal door frame having post and header components each formed of a single piece of metal stock, thereby precluding need for additional seam welding along the lengths of the components.
It is a further object of the invention to provide an improved universal door frame having a relatively wide horizontal width between posts and a relatively tall height between sill and header, for maximizing the size of objects placed within the trailer.
An additional object of the invention is to provide an improved door frame including means for motorizing an overhead door provided therewith.
Still another object of the invention is to provide an improved door frame with a motorized overhead door in which the motor and lifting means are disposed within the header of the door frame.
It is an object of the invention to provide improved elements and arrangements thereof in an apparatus for the purposes described which is inexpensive, dependable and fully effective in accomplishing its intended purposes.
These and other objects of the present invention will become readily apparent upon further review of the following specification and drawings.